XDEBUG EXTENSION FOR PHP | DOCUMENTATION
Xdebug provides an interface for debugger clients that interact with running PHP scripts. This section explains how to set-up PHP and Xdebug to allow this, and introduces a few clients.
Xdebug's (remote) debugger allows you to examine data structure, interactively walk through your and debug your code. The protocol that is being used is open, and is called DBGp. This protocol is implemented in Xdebug 2, and replaces an older GDB-like protocol that is no longer supported.
Xdebug 2 is bundled with a simple command line client for the DBGp protocol. There are a few other client implementations (both free and commercial) as well. I am not the author of any of those, so please refer to the original authors for support:
A simple command line client for debugging is bundled with Xdebug in the
Starting The Debugger
In order to enable Xdebug's debugger you need to make some configuration settings in php.ini. These settings are xdebug.remote_enable to enable the debugger, xdebug.remote_host and xdebug.remote_port to configure the IP address and port where the debugger should connect to. There is also a xdebug.remote_connect_back setting that can be used if your development server is shared with multiple developers.
If you want the debugger to initiate a session when an error situation occurs (PHP error or exception) then you also need to change the xdebug.remote_mode setting. Allowed values for this setting are "req" (the default) which makes the debugger initiate a session as soon as a script is started, or "jit" when a session should only be initiated on an error.
After made all those settings Xdebug will still not start a debugging session automatically when a script is run. You need to activate Xdebug's debugger and you can do that in three ways:
Before you start your script you will need to tell your client that it can receive debug connections, please refer to the documentation of the specific client on how to do this. To use the bundled client simply start it after compiling and installing it. You can start it by running "debugclient".
When the debugclient starts it will show the following information and then waits until a connection is initiated by the debug server:
Xdebug Simple DBGp client (0.10.0) Copyright 2002-2007 by Derick Rethans. - libedit support: enabled Waiting for debug server to connect.
After a connection is made the output of the debug server is shown:
Connect <?xml version="1.0" encoding="iso-8859-1"?> <init xmlns="urn:debugger_protocol_v1" xmlns:xdebug="http://xdebug.org/dbgp/xdebug" fileuri="file:///home/httpd/www.xdebug.org/html/docs/index.php" language="PHP" protocol_version="1.0" appid="13202" idekey="derick"> <engine version="2.0.0RC4-dev"><![CDATA[Xdebug]]></engine> <author><![CDATA[Derick Rethans]]></author> <url><![CDATA[http://xdebug.org]]></url> <copyright><![CDATA[Copyright (c) 2002-2007 by Derick Rethans]]></copyright> </init> (cmd)
Now you can use the commandset as explained on the DBGp documentation page. When the script ends the debug server disconnects from the client and the debugclient resumes with waiting for a new connection.
With a static IP/single developer
With remote debugging, Xdebug embedded in PHP acts like the client, and the IDE as the server. The following animation shows how the communication channel is set-up:
With an unknown IP/multiple developers
If xdebug.remote_connect_back is used, the set-up is slightly different:
HTTP Debug Sessions
Xdebug contains functionality to keep track of a debug session when started through a browser: cookies. This works like this:
Multiple Users Debugging
Xdebug only allows you to specify one IP address to connect to with xdebug.remote_host) while doing remote debugging. It does not automatically connect back to the IP address of the machine the browser runs on, unless you use xdebug.remote_connect_back.
If all of your developers work on different projects on the same (development)
server, you can make the xdebug.remote_host setting for each directory
through Apache's .htaccess functionality by using
There are two solutions to this. First of all, you can use a DBGp proxy. For an overview on how to use this proxy, please refer to the article at Debugging with multiple users. You can download the proxy on ActiveState's web site as part of the python remote debugging package. There is some more documentation in the Komodo FAQ.
Secondly you can use the xdebug.remote_connect_back setting that was introduced in Xdebug 2.1.
Xdebug's implementation of the
xdebug.extended_infoType: integer, Default value: 1
Controls whether Xdebug should enforce 'extended_info' mode for the PHP parser; this allows Xdebug to do file/line breakpoints with the remote debugger. When tracing or profiling scripts you generally want to turn off this option as PHP's generated oparrays will increase with about a third of the size slowing down your scripts. This setting can not be set in your scripts with ini_set(), but only in php.ini.
xdebug.idekeyType: string, Default value: *complex*
Controls which IDE Key Xdebug should pass on to the DBGp debugger handler. The default is based on environment settings. First the environment setting DBGP_IDEKEY is consulted, then USER and as last USERNAME. The default is set to the first environment variable that is found. If none could be found the setting has as default ''. If this setting is set, it always overrides the environment variables.
xdebug.remote_addr_headerType: string, Default value: "", Introduced in Xdebug >= 2.4
If xdebug.remote_addr_header is configured to be a non-empty string, then the value is used as key in the $SERVER superglobal array to determine which header to use to find the IP address or hostname to use for 'connecting back to'. This setting is only used in combination with xdebug.remote_connect_back and is otherwise ignored.
xdebug.remote_autostartType: boolean, Default value: 0
Normally you need to use a specific HTTP GET/POST variable to start remote debugging (see Remote Debugging). When this setting is set to 1, Xdebug will always attempt to start a remote debugging session and try to connect to a client, even if the GET/POST/COOKIE variable was not present.
xdebug.remote_connect_backType: boolean, Default value: 0, Introduced in Xdebug >= 2.1
If enabled, the xdebug.remote_host setting is ignored and Xdebug will try to connect to the client that made the HTTP request. It checks the $_SERVER['HTTP_X_FORWARDED_FOR'] and $_SERVER['REMOTE_ADDR'] variables to find out which IP address to use.
If xdebug.remote_addr_header is configured, then the $SERVER variable with the configured name will be checked before the $_SERVER['HTTP_X_FORWARDED_FOR'] and $_SERVER['REMOTE_ADDR'] variables.
This setting does not apply for debugging through the CLI, as the $SERVER header variables are not available there.
Please note that there is no filter available, and anybody who can connect to the webserver will then be able to start a debugging session, even if their address does not match xdebug.remote_host.
xdebug.remote_cookie_expire_timeType: integer, Default value: 3600, Introduced in Xdebug >= 2.1
This setting can be used to increase (or decrease) the time that the remote debugging session stays alive via the session cookie.
xdebug.remote_enableType: boolean, Default value: 0
This switch controls whether Xdebug should try to contact a debug client which is listening on the host and port as set with the settings xdebug.remote_host and xdebug.remote_port. If a connection can not be established the script will just continue as if this setting was 0.
xdebug.remote_handlerType: string, Default value: dbgp
Can be either 'php3' which selects the old PHP 3 style debugger output, 'gdb' which enables the GDB like debugger interface or 'dbgp' - the debugger protocol. The DBGp protocol is the only supported protocol.
Note: Xdebug 2.1 and later only support 'dbgp' as protocol.
xdebug.remote_hostType: string, Default value: localhost
Selects the host where the debug client is running, you can either use a host name or an IP address. This setting is ignored if xdebug.remote_connect_back is enabled.
xdebug.remote_logType: string, Default value:
If set to a value, it is used as filename to a file to which all remote debugger communications are logged. The file is always opened in append-mode, and will therefore not be overwritten by default. There is no concurrency protection available. The format of the file looks something like:
Log opened at 2007-05-27 14:28:15 -> <init xmlns="urn:debugger_protocol_v1" xmlns:xdebug="http://xdebug.org/dbgp/x ... ight></init> <- step_into -i 1 -> <response xmlns="urn:debugger_protocol_v1" xmlns:xdebug="http://xdebug.org/db ... ></response>
xdebug.remote_modeType: string, Default value: req
Selects when a debug connection is initiated. This setting can have two different values:
xdebug.remote_portType: integer, Default value: 9000
The port to which Xdebug tries to connect on the remote host. Port 9000 is the default for both the client and the bundled debugclient. As many clients use this port number, it is best to leave this setting unchanged.
Emits a breakpoint to the debug client.
This function makes the debugger break on the specific line as if a normal file/line breakpoint was set on this line.
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